Efficient coding of global motion vectors

ABSTRACT

A decoder includes circuitry configured to receive a bitstream, extract a residual of a control point motion vector for a current frame and from the bitstream, and combine the residual of the control point motion vector with a prediction of the control point motion vector for the current frame. Related apparatus, systems, techniques and articles are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of InternationalApplication No. PCT/US20/29936, filed on Apr. 24, 2020 and entitled“EFFICIENT CODING OF GLOBAL MOTION VECTORS,” which claims the benefit ofpriority of U.S. Provisional Patent Application Ser. No. 62/838,521,filed on Apr. 25, 2019, and titled “EFFICIENT CODING OF GLOBAL MOTIONVECTORS.” Each of International Application No. PCT/US20/29936 and U.S.Provisional Patent Application Ser. No. 62/838,521 is incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of videocompression. In particular, the present invention is directed toefficient coding of global motion vectors.

BACKGROUND

A video codec can include an electronic circuit or software thatcompresses or decompresses digital video. It can convert uncompressedvideo to a compressed format or vice versa. In the context of videocompression, a device that compresses video (and/or performs somefunction thereof) can typically be called an encoder, and a device thatdecompresses video (and/or performs some function thereof) can be calleda decoder.

A format of the compressed data can conform to a standard videocompression specification. The compression can be lossy in that thecompressed video lacks some information present in the original video. Aconsequence of this can include that decompressed video can have lowerquality than the original uncompressed video because there isinsufficient information to accurately reconstruct the original video.

There can be complex relationships between the video quality, the amountof data used to represent the video (e.g., determined by the bit rate),the complexity of the encoding and decoding algorithms, sensitivity todata losses and errors, ease of editing, random access, end-to-end delay(e.g., latency), and the like.

Motion compensation can include an approach to predict a video frame ora portion thereof given a reference frame, such as previous and/orfuture frames, by accounting for motion of the camera and/or objects inthe video. It can be employed in the encoding and decoding of video datafor video compression, for example in the encoding and decoding usingthe Motion Picture Experts Group (MPEG)-2 (also referred to as advancedvideo coding (AVC) and H.264) standard. Motion compensation can describea picture in terms of the transformation of a reference picture to thecurrent picture. The reference picture can be previous in time whencompared to the current picture, from the future when compared to thecurrent picture. When images can be accurately synthesized frompreviously transmitted and/or stored images, compression efficiency canbe improved.

SUMMARY OF THE DISCLOSURE

In an aspect, a decoder includes circuitry configured to receive abitstream, extract a residual of a control point motion vector for acurrent frame from the bitstream, and combine the residual of thecontrol point motion vector with a prediction of the control pointmotion vector for the current frame.

In another aspect, a method includes receiving, by a decoder, abitstream. The method includes extracting a residual of a control pointmotion vector for a current frame and from the bitstream. The methodincludes combining the residual of the control point motion vector witha prediction of the control point motion vector for the current frame.

These and other aspects and features of non-limiting embodiments of thepresent invention will become apparent to those skilled in the art uponreview of the following description of specific non-limiting embodimentsof the invention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a diagram illustrating motion vectors of an example frame withglobal and local motion;

FIG. 2 illustrates three example motion models that can be utilized forglobal motion including their index value (0, 1, or 2);

FIG. 3 is a process flow diagram according to some exampleimplementations of the current subject matter;

FIG. 4 is a system block diagram of an example decoder according to someexample implementations of the current subject matter;

FIG. 5 is a process flow diagram according to some exampleimplementations of the current subject matter;

FIG. 6 is a system block diagram of an example encoder according to someexample implementations of the current subject matter; and

FIG. 7 is a block diagram of a computing system that can be used toimplement any one or more of the methodologies disclosed herein and anyone or more portions thereof.

The drawings are not necessarily to scale and may be illustrated byphantom lines, diagrammatic representations and fragmentary views. Incertain instances, details that are not necessary for an understandingof the embodiments or that render other details difficult to perceivemay have been omitted.

DETAILED DESCRIPTION

“Global motion” in video refers to motion and/or a motion model commonto all pixels of a region, where a region may be a picture, a frame, orany portion of a picture or frame such as a block, CTU, or other subsetof contiguous pixels. Global motion may be caused by camera motion; forexample and without limitation, camera panning and zooming may createmotion in a frame that may typically affect the entire frame. Motionpresent in portions of a video may be referred to as local motion. Localmotion may be caused by moving objects in a scene, such as withoutlimitation an object moving from left to right in the scene. Videos maycontain a combination of local and global motion. Some implementationsof the current subject matter may provide for efficient approaches tocommunicate global motion to the decoder and use of global motionvectors in improving compression efficiency.

FIG. 1 is a diagram illustrating exemplary embodiments of motion vectorsof an exemplary frame 100 with global and local motion. Frame 100 mayinclude a number of blocks of pixels illustrated as squares, and theirassociated motion vectors illustrated as arrows. Squares (e.g., blocksof pixels) with arrows pointing up and to the left may indicate blockswith motion that may be considered to be global motion and squares witharrows pointing in other directions (indicated by 104) indicate blockswith local motion. In the illustrated example of FIG. 1, many of theblocks have same global motion. Signaling global motion in a header,such as a picture parameter set (PPS) or sequence parameter set (SPS),and using signaled global motion may reduce motion vector informationneeded by blocks and may result in improved prediction. Although forillustrative purposes examples described below refer to determinationand/or application of global or local motion vectors at a block level,global motion vectors may be determined and/or applied for any region ofa frame and/or picture, including regions made up of multiple blocks,regions bounded by any geometric form such as without limitation regionsdefined by geometric and/or exponential coding in which one or morelines and/or curves bounding the shape may be angled and/or curved,and/or an entirety of a frame and/or picture. Although signaling isdescribed herein as being performed at a frame level and/or in a headerand/or parameter set of a frame, signaling may alternatively oradditionally be performed at a sub-picture level, where a sub-picturemay include any region of a frame and/or picture as described above.

As an example, and still referring to FIG. 1, simple translationalmotion may be described using a motion vector (MV) with two componentsMVx, MVy that describes displacement of blocks and/or pixels in acurrent frame. More complex motion such as rotation, zooming, andwarping may be described using affine motion vectors, where an “affinemotion vector,” as used in this disclosure, is a vector describing auniform displacement of a set of pixels or points represented in a videopicture and/or picture, such as a set of pixels illustrating an objectmoving across a view in a video without changing apparent shape duringmotion. Some approaches to video encoding and/or decoding may use4-parameter or 6-parameter affine models for motion compensation ininter picture coding.

For example, a six parameter affine motion may be described as:

x′=ax+by+c

y′=dx+ey+f

A four parameter affine motion may be described as:

x′=ax+by+c

y′=−bx+ay+f

where (x,y) and (x′,y′) are pixel locations in current and referencepictures, respectively; a, b, c, d, e, and f are the parameters of theaffine motion model.

With continued reference to FIG. 1, parameters used describe affinemotion may be signaled to a decoder to apply affine motion compensationat the decoder. In some approaches, motion parameters may be signaledexplicitly or by signaling translational control point motion vectors(CPMVs) and then deriving the affine motion parameters fromtranslational motion vectors. Two control point motion vectors (CPMVs)may be utilized to derive affine motion parameters for a four-parameteraffine motion model and three control point translational motion vectors(CPMVs) may be utilized to obtain parameters for a six-parameter motionmodel. Signaling affine motion parameters using control point motionvectors may allow use of efficient motion vector coding methods tosignal affine motion parameters.

In some implementations, and still referring to FIG. 1, global motionsignaling may be included in a header, such as the PPS or SPS. Globalmotion may vary from picture to picture. Motion vectors signaled inpicture headers may describe motion relative to previously decodedframes. In some implementations, global motion may be translational oraffine. Motion model (e.g., number of parameters, whether the model isaffine, translational, or other) used may also be signaled in a pictureheader. FIG. 2 illustrates three example motion models 200 that may beutilized for global motion including their index value (0, 1, or 2).

Continuing to refer to FIG. 2, PPSs may be used to signal parametersthat may change between pictures of a sequence. Parameters that remainthe same for a sequence of pictures may be signaled in a sequenceparameter set to reduce the size of PPS and reduce video bitrate. Anexample picture parameter set (PPS) is shown in table 1:

Descriptor pic_parameter_set_rbsp( ) { pps_pic_parameter_set_id ue(v)pps_seq_parameter_set_id u(4) mixed_nalu_types_in_pic_flag u(1)pic_width_in_luma_samples ue(v) pic_height_in_luma_samples ue(v)pps_conformance_window_flag u(1) if( pps_conformance_window_flag ) {pps_conf_win_left_offset ue(v) pps_conf_win_right_offset ue(v)pps_conf_win_top_offset ue(v) pps_conf_win_bottom_offset ue(v) }scaling_window_explicit_signalling_flag u(1) if(scaling_window_explicit_signalling_flag ) { scaling_win_left_offsetue(v) scaling_win_right_offset ue(v) scaling_win_top_offset ue(v)scaling_win_bottom_offset ue(v) } output_flag_present_flag u(1)subpic_id_mapping_in_pps_flag u(1) if( subpic_id_mapping _in_pps_flag ){ pps_num_subpics_minus1 ue(v) pps_subpic_id_len_minus1 ue(v) for( i =0; i <= pps_num_subpic_minus1; i++ ) pps_subpic_id[ i ] u(v) }no_pic_partition_flag u(1) if( !no_pic_partition_flag ) {pps_log2_ctu_size_minus5 u(2) num_exp_tile_columns_minus1 ue(v)num_exp_tile_rows_minus1 ue(v) for( i = 0; i <=num_exp_tile_columns_minus1; i++ ) tile_column_width_minus1[ i ] ue(v)for(i = 0; i <= num_exp_tile_rows_minus1; i++ ) tile_row_height_minus1[i ] ue(v) if( NumTilesInPic > 1 ) rect_slice_flag u(1) if(rect_slice_flag ) single_slice_per_subpic_flag u(1) if( rect_slice_flag&& !single_slice_per_subpic_flag ) { num_slices_in_pic_minus1 ue(v) if(num_slices_in_pic_minus1 > 0 ) tile_idx_delta_present_flag u(1) for( i =0; i < num_slices_in_pic_minus1; i++ ) { if( NumTileColumns > 1 )slice_width_in_tiles_minus1[ i ] ue(v) if( NumTileRows > 1 && (tile_idx_delta_present_flag | | SliceTopLeftTileIdx[ i ] %NumTileColumns == 0 ) ) slice_height_in_tiles_minus1[ i ] ue(v) if(slice_width_in_tiles_minus1[ i ] == 0 && slice_height_in_tiles_minus1[ i] == 0 && RowHeight[ SliceTopLeftTileIdx[ i ] / NumTileColumns ] > 1 ) {num_exp_slices_in_tile[ i ] ue(v) for( j = 0; j <num_exp_slices_in_tile[ i ]; j++ ) exp_slice_height_in_ctus_minus1[ i ][j ] ue(v) i += NumSlicesInTile[ i ] − 1 } if( tile_idx_delta_presentflag && i < num_slices_in_pic_minus1 ) tile_idx_delta[ i ] se(v) } }loop_filter_across_tiles_enabled_flag u(1)loop_filter_across_slices_enabled_flag u(1) } cabac_init_present_flagu(1) for( i = 0; i < 2; i++ ) num_ref_idx_default_active_minus1[ i ]ue(v) rpl1_idx_present_flag u(1) init_qp_minus26 se(v)cu_qp_delta_enabled_flag u(1) pps_chroma_tool_offsets_present_flag u(1)if( pps_chroma_tool_offsets_present_flag ) { pps_cb_qp_offset se(v)pps_cr_qp_offset se(v) pps_joint_cbcr_qp_offset_present_flag u(1) if(pps_joint_cbcr_qp_offset_present_flag ) pps_joint_cbcr_qp_offset_valuese(v) pps_slice_chroma_qp_offsets_present_flag u(1)pps_cu_chroma_qp_offset_list_enabled_flag u(1) } if(pps_cu_chroma_qp_offset_list_enabled_flag ) {chroma_qp_offset_list_len_minus1 ue(v) for( i = 0; i <=chroma_qp_offset_list_len_minus1; i++ ) { cb_qp_offset_list[ i ] se(v)cr_qp_offset_list[ i ] se(v) if( pps_joint_cbcr_qp_offset_present_flag )joint_cbcr_qp_offset_list[ i ] se(v) } } pps_weighted_pred_flag u(1)pps_weighted_bipred_flag u(1) deblocking_filter_control_present_flagu(1) if( deblocking_filter_control_present_flag ) {deblocking_filter_override_enabled_flag u(1)pps_deblocking_filter_disabled_flag u(1) if(!pps_deblocking_filter_disabled_flag ) { pps_beta_offset_div2 se(v)pps_tc_offset_div2 se(v) pps_cb_beta_offset_div2 se(v)pps_cb_tc_offset_div2 se(v) pps_cr_beta_offset_div2 se(v)pps_cr_tc_offset_div2 se(v) } } rpl_info_in_ph_flag u(1) if(deblocking_filter_override_enabled_flag ) dbf_info_in_ph_flag u(1)sao_info_in_ph_flag u(1) alf_info_in_ph_flag u(1) if( (pps_weighted_pred_flag | | pps_weighted_bipred_flag ) &&rpl_info_in_ph_flag ) wp_info_in_ph_flag u(1) qp_delta_info_in_ph_flagu(1) pps_ref_wraparound_enabled_flag u(1) if(pps_ref_wraparound_enabled_flag ) pps_ref_wraparound_offset ue(v)picture_header_extension_present_flag u(1)slice_header_extension_present_flag u(1) pps_extension_flag u(1) if(pps_extension_flag ) while( more_rbsp_data( ) ) pps_extension_data_flagu(1) rbsp_trailing_bits( ) }

Still referring to FIG. 2, additional fields may be added to the PPS tosignal global motion. In case of global motion, the presence of globalmotion parameters in sequence of pictures can be signaled in a SPS andthe PPS references the SPS by SPS ID. The SPS in some approaches todecodingmaybemodifiedtoaddafieldtosignalpresenceofglobalmotionparametersinSPS. For example a one-bit field may be added to the SPS. Ifglobal_motion_present bit is 1, global motion related parameters may beexpected in a PPS; if global_motion_present bit is 0, no global motionparameter related fields may be present in the PPS. For example, the PPSof table 1 may be extended to include a global_motion_present field, forexample, as shown in table 2:

Descriptor sequence_parameter_set_rbsp( ) {sps_sequence_parameter_set_id ue(v) • • • global_motion_present u(1)rbsp_trailing_bits( ) }

Similarly, the PPS may include a pps_global_motion_parameters field fora frame, for example as shown in table 3:

Descriptor pic_parameter_set_rbsp( ) { pps_pic_parameter_set_id ue(v)pps_seq_parameter_set_id ue(v) • • • pps_global_motion_parameters ( )rbsp_trailing_bits( ) }

In more detail, the PPS may include fields to characterize global motionparameters using control point motion vectors, for example as shown intable 4:

Descriptor pps_global_motion_parameters ( ) { motion_model_used u(2)mv0_x se(v) mv1_y se(v) if(motion_model_used == 1){ mv1_x se(v) mv1_yse(v) } if(motion_model_used == 2){ mv2_x se(v) mv2_y se(v) } }

As a further non-limiting example, Table 5 below may represent anexemplary SPS:

Descriptor seq_parameter_set_rbsp( ) { sps_seq_parameter_set_id u(4)sps_video_parameter_set_id u(4) sps_max_sublayers_minus1 u(3)sps_reserved_zero_4bits u(4) sps_ptl_dpb_hrd_params_present_flag u(1)if( sps_ptl_dpb_hrd_params_present_flag ) profile_tier_level( 1,sps_max_sublayers_minus1 ) gdr_enabled_flag u(1) chroma_format_idc u(2)if( chroma_format_idc == 3 ) separate_colour_plane_flag u(1)res_change_in_clvs_allowed_flag u(1) pic_width_max_in_luma_samples ue(v)pic_height_max_in_luma_samples ue(v) sps_conformance_window_flag u(1)if( sps_conformance_window_flag ) { sps_conf_win_left_offset ue(v)sps_conf_win_right_offset ue(v) sps_conf_win_top_offset ue(v)sps_conf_win_bottom_offset ue(v) } sps_log2_ctu_size_minus5 u(2)subpic_info_present_flag u(1) if( subpic_info_present_flag ) {sps_num_subpics_minus1 ue(v) sps_independent_subpics_flag u(1) for( i =0; sps_num_subpics_minus1 > 0 && i <= sps_num_subpics_minus1; i++ ) {if( i > 0 && pic_width_max_in_luma_samples > CtbSizeY )subpic_ctu_top_left_x[ i ] u(v) if( i > 0 &&pic_height_max_in_luma_samples > CtbSizeY ) { subpic_ctu_top_left_y[ i ]u(v) if( i < sps_num_subpics_minus1 && pic_width_max_in_luma_samples >CtbSizeY ) subpic_width_minus1[ i ] u(v) if( i < sps_num_subpics_minus1&& pic_height_max_in_luma_samples > CtbSizeY ) subpic_height_minus1[ i ]u(v) if( !sps_independent_subpics_flag ) { subpic_treated_as_pic_flag[ i] u(1) loop_filter_across_subpic_enabled_flag[ i ] u(1) } }sps_subpic_id_len_minus1 ue(v)subpic_id_mapping_explicitly_signalled_flag u(1) if(subpic_id_mapping_explicitly_signalled_flag ) {subpic_id_mapping_in_sps_flag u(1) if( subpic_id_mapping_in_sps_flag )for(i = 0; i <= sps_num_subpics_minus1; i++ ) sps_subpic_id[ i ] u(v) }} bit_depth_minus8 ue(v) sps_entropy_coding_sync_enabled_flag u(1) if(sps_entropy_coding_sync_enabled_flag )sps_wpp_entry_point_offsets_present_flag u(1) sps_weighted_pred_flagu(1) sps_weighted_bipred_flag u(1) log2_max_pic_order_cnt_lsb_minus4u(4) sps_poc_msb_flag u(1) if( sps_poc_msb_flag ) poc_msb_len_minus1ue(v) num_extra_ph_bits_bytes u(2) extra_ph_bits_struct(num_extra_ph_bits_bytes ) num_extra_sh_bits_bytes u(2)extra_sh_bits_struct( num_extra_sh_bits_bytes ) if(sps_max_sublayers_minus1 > 0 ) sps_sublayer_dpb_params_flag u(1) if(sp_ptl_dpb_hrd_params_present_flag ) dpb_parameters(sps_max_sublayers_minus1, sps_sublayer_dpb_params_flag )long_term_ref_pics_flag u(1) inter_layer_ref_pics_present_flag u(l)sps_idr_rpl_present_flag u(1) rpl1_same_as_rpl0_flag u(1) for( i = 0; i< rpl1_same_as_rpl0_flag ? 1 : 2; i++ ) { num_ref_pic_lists_in_sps[ i ]ue(v) for( j = 0; j < num_ref_pic_lists_in_sps[ i ]; j++)ref_pic_list_struct( i, j ) } if( ChromaArrayType != 0 )qtbtt_dual_tree_intra_flag u(1) log2_min_luma_coding_block_size_minus2ue(v) partition_constraints_override_enabled_flag u(1)sps_log2_diff_min_qt_min_cb_intra_slice_luma ue(v)sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v) if(sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {sps_log2_diff_max_bt_min_qt_intra_slice_luma ue(v)sps_log2_diff_max_tt_min_qt_intra_slice_luma ue(v) }sps_log2_diff_min_qt_min_cb_inter_slice ue(v)sps_max_mtt_hierarchy_depth_inter_slice ue(v) if(sps_max_mtt_hierarchy_depth_inter_slice != 0 ) {sps_log2_diff_max_bt_min_qt_inter_slice ue(v)sps_log2_diff_max_tt_min_qt_inter_slice ue(v) } if(qtbtt_dual_tree_intra_flag ) {sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v)sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v) if(sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {sps_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v)sps_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v) } }sps_max_luma_transform_size_64_flag u(1) if( ChromaArrayType != 0 ) {sps_joint_cbcr_enabled_flag u(1) same_qp_table_for_chroma u(1)numQpTables = same_qp_table_for_chroma ? 1 : (sps_joint_cbcr_enabled_flag ? 3 : 2 ) for( i = 0; i < numQpTables; i++ ){ qp_table_start_minus26[ i ] se(v) num_points_in_qp_table_minus1[ i ]ue(v) for( j = 0; j <= num_points_in_qp_table_minus1[ i ]; j++ ) {delta_qp_in_val_minus1[ i ][ j ] ue(v) delta_qp_diff_val[ i ][ j ] ue(v)} } } sps_sao_enabled_flag u(1) sps_alf_enabled_flag u(1) if(sps_alf_enabled_flag && ChromaArrayType != 0 ) sps_ccalf_enabled_flagu(1) sps_transform_skip_enabled_flag u(1) if(sps_transform_skip_enabled_flag ) { log2_transform_skip_max_size_minus2ue(v) sps_bdpcm_enabled_flag u(1) } sps_ref_wraparound_enabled_flag u(1)sps_temporal_mvp_enabled_flag u(1) if( sps_temporal_mvp_enabled_flag )sps_sbtmvp_enabled_flag u(1) sps_amvr_enabled_flag u(1)sps_bdof_enabled_flag u(1) if( sps_bdof_enabled_flag )sps_bdof_pic_present_flag u(1) sps_smvd_enabled_flag u(1)sps_dmvr_enabled_flag u(1) if( sps_dmvr_enabled_flag )sps_dmvr_pic_present_flag u(1) sps_mmvd_enabled_flag u(1)sps_isp_enabled_flag u(1) sps_mrl_enabled_flag u(1) sps_mip_enabled_flagu(1) if( ChromaArrayType != 0 ) sps_cclm_enabled_flag u(1) if(chroma_format_idc == 1 ) { sps_chroma_horizontal_collocated_flag u(1)sps_chroma_vertical_collocated_flag u(1) } sps_mts_enabled_flag u(1) if(sps_mts_enabled_flag ) { sps_explicit_mts_intra_enabled_flag u(1)sps_explicit_mts_inter_enabled_flag u(1) } six_minus_max_num_merge_candue(v) sps_sbt_enabled_flag u(1) sps_affine_enabled_flag u(1) if(sps_affine_enabled_flag ) { five_minus_max_num_subblock_merge_cand ue(v)sps_affine_type_flag u(1) if( sps_amvr_enabled_flag )sps_affine_amvr_enabled_flag u(1) sps_affine_prof_enabled_flag u(1) if(sps_affine_prof_enabled_flag ) sps_prof_pic_present_flag u(1) }sps_palette_enabled_flag u(1) if( ChromaArrayType == 3 &&!sps_max_luma_transform_size_64_flag ) sps_act_enabled_flag u(1) if(sps_transform_skip_enabled_flag | | sps_palette_enabled_flag )min_qp_prime_ts_minus4 ue(v) sps_bcw_enabled_flag u(1)sps_ibc_enabled_flag u(1) if( sps_ibc_enabled_flag )six_minus_max_num_ibc_merge_cand ue(v) sps_ciip_enabled_flag u(1) if(sps_mmvd_enabled_flag ) sps_fpel_mmvd_enabled_flag u(1) if(MaxNumMergeCand >= 2 ) { sps_gpm_enabled_flag u(1) if(sps_gpm_enabled_flag && MaxNumMergeCand >= 3 )max_num_merge_cand_minus_max_num_gpm_cand ue(v) } sps_lmcs_enabled_flagu(1) sps_lfnst_enabled_flag u(1) sps_ladf_enabled_flag u(1) if(sps_ladf_enabled_flag ) { sps_num_ladf_intervals_minus2 u(2)sps_ladf_lowest_interval_qp_offset se(v) for( i = 0; i <sps_num_ladf_intervals_minus2 + 1; i++ ) { sps_ladf_qp_offset[ i ] se(v)sps_ladf_delta_threshold_minus1[ i ] ue(v) } }log2_parallel_merge_level_minus2 ue(v)sps_explicit_scaling_list_enabled_flag u(1) sps_dep_quant_enabled_flagu(1) if( !sps_dep_quant_enabled_flag ) sps_sign_data_hiding_enabled_flagu(1) sps_virtual_boundaries_enabled_flag u(1) if(sps_virtual_boundaries_enabled_flag ) {sps_virtual_boundaries_present_flag u(1) if(sps_virtual_boundaries_present_flag ) { sps_num_ver_virtual_boundariesu(2) for( i = 0; i < sps_num_ver_virtual_boundaries; i++ )sps_virtual_boundaries_pos_x[ i ] u(13) sps_num_hor_virtual_boundariesu(2) for( i = 0; i < sps_num_hor_virtual_boundaries; i++ )sps_virtual_boundaries_pos_y[ i ] u(13) } } if(sps_ptl_dpb_hrd_params_present_flag ) {sps_general_hrd_params_present_flag u(1) if(sps_general_hrd_params_present_flag ) { general hrd_parameters( ) if(sps_max_sublayers_minus1 > 0 ) sps_sublayer_cpb_params_present_flag u(1)firstSubLayer = sps_sublayer_cpb_params_present_flag ? 0 :sps_max_sublayers_minus1 ols_hrd_parameters( firstSubLayer, sps_maxsublayers_minus1 ) } } field_seq_flag u(1) vui_parameters_present_flagu(1) if( vui_parameters_present_flag ) vui_parameters( ) /* Specified inITU-T H.SEI | ISO/IEC 23002-7 */ sps_extension_flag u(1) if(sps_extension_flag ) while( more_rbsp_data( ) ) sps_extension_data_flagu(1) rbsp_trailing_bits( ) }

An SPS table as above may be expanded as described above to incorporatea global motion present indicator as shown in Table 6:

Descriptor sequence_parameter_set_rbsp( ) {sps_sequence_parameter_set_id ue(v) • • • global_motion_present u(1)rbsp_trailing_bits( ) }

Additional fields may be incorporated in an SPS to reflect furtherindicators as described in this disclosure.

In an embodiment, and still referring to FIG. 2, ansps_affine_enabled_flag in a PPS and/or SPS may specify whether affinemodel based motion compensation may be used for inter prediction. Ifsps_affine_enabled_flag is equal to 0, the syntax may be constrainedsuch that no affine model based motion compensation is used in the codelater video sequence (CLVS), and inter_affine_flag andcu_affine_type_flag may not be present in coding unit syntax of theCLVS. Otherwise (sps_affine_enabled_flag is equal to 1), affine modelbased motion compensation can be used in the CLVS.

Continuing to refer to FIG. 2, sps_affine_type_flag in a PPS and/or SPSmay specify whether 6-parameter affine model based motion compensationmay be used for inter prediction. If sps_affine_type_flag is equal to 0,syntax may be constrained such that no 6-parameter affine model basedmotion compensation is used in the CLVS, and cu_affine_type_flag may notpresent in coding unit syntax in the CLVS. Otherwise(sps_affine_type_flag equal to 1), 6-parameter affine model based motioncompensation may be used in CLVS. When not present, the value ofsps_affine_type_flag may be inferred to be equal to 0.

Still referring to FIG. 2, translational CPMVs may be signaled in a PPS.Control points may be predefined. For example, control point MV 0 may berelative to atop left corner of a picture, MV 1 may be relative to atopright corner, and MV 3 may be relative to a bottom left corner of apicture. Table 4 illustrates an example approach for signaling CPMV datadepending on the motion model used.

In an exemplary embodiment, and still referring to FIG. 2, an arrayamvr_precision_idx, which may be signaled in coding unit, coding tree,or the like, may specify a resolution AmvrShift of a motion vectordifference, which may be defined as a non-limiting example as shown inTable 7 as shown below. Array indices x0, y0 may specify the location(x0, y0) of a top-left luma sample of a considered coding block relativeto a top-left luma sample of the picture; whenamvr_precision_idx[x0][y0] is not present, it may be inferred to beequal to 0. Where an inter_affine_flag[x0][y0] is equal to 0, variablesMvdL0[x0][y0][0], MvdL0[x0][y0][1], MvdL1[x0][y0][0], MvdL1[x0][y0][1]representing modsion vector difference values corresponding toconsidered block, may be modified by shifting such values by AmvrShift,for instance using MvdL0[x0][y0][0]=MvdL0[x0][y0][0]<<AmvrShift;MvdL0[x0][y0][1]=MvdL0[x0][y0][1]<<AmvrShift;MvdL1[x0][y0][0]=MvdL1[x0][y0][0]<<AmvrShift; andMvdL1[x0][y0][1]=MvdL1[x0][y0][1]<<AmvrShift. Whereinter_affine_flag[x0][y0] is equal to 1, variablesMvdCpL0[x0][y0][0][0], MvdCpL0[x0][y0][0][1], MvdCpL0[x0][y0][1][0],MvdCpL0[x0][y0][1][1], MvdCpL0[x0][y0][2][0] and MvdCpL0[x0][y0][2][1]may be modified via shifting, for instance as follows:MvdCpL0[x0][y0][0][0]=MvdCpL0[x0][y0][0][0]<<AmvrShift; MvdCpL1[x0][y0][0][1]=MvdCpL1[x0][y0][0][1]<<AmvrShift;MvdCpL0[x0][y0][1][0]=MvdCpL0[x0][y0][1][0]<<AmvrShift; MvdCpL1[x0][y0][1][1]=MvdCpL1[x0][y0][1][1]<<AmvrShift;MvdCpL0[x0][y0][2][0]=MvdCpL0[x0][y0][2][0]<<AmvrShift; andMvdCpL1[x0][y0] [2][1]=MvdCpL1[x0][y0][2][1]<<AmvrShift

AmvrShift CuPredMode[ inter_affine_flag ==0 chType ][ x0 ] &&CuPredMode[ chType ][ x0 ] amvr_flag amvr_precision_id inter_affine_flag==1 [ y0 ] == MODE_IBC ) [y0] != MODE_IBC 0 — 2 (1/4 luma sample)  — 2(1/4 luma sample) 1 0 0 (1/16 luma sample) 4 (1 luma sample)  3 (1/2luma sample) 1 1 4 (1 luma sample)   6 (4 luma samples) 4 (1 lumasample)  1 2 — 6 (4 luma samples) 

With continued reference to FIG. 2, global motion may be relative to apreviously coded frame. When only one set of global motion parametersare present, motion may be relative to a frame that is presentedimmediately before current frame.

Still referring to FIG. 2. some implementations of current subjectmatter may include predicting global motion vectors in a current framefrom previously encoded global motion vectors of a previous frame toimprove compression.

Continuing to refer to FIG. 2, a current picture being encoded as aninter picture may use motion estimation to improve compression. Globalmotion vectors for a current picture may be signaled in a PPS. In someapproaches to video compression, when encoding global motion parameters(e.g., control point motion vectors) in a current frame, the followinginformation may already be decoded and available: 1) global motionparameters from a previous frame; 2) global motion parameters relativeto available reference pictures in List0 that are already encoded in acurrent frame; and 3) control point motion vectors in global motionparameters being coded.

Still referring to FIG. 2, predicted motion vector (PMV) of controlpoint motion vectors (CPMV) may be determined from previously codedmotion vectors and the difference between the CPMV and PMV may be codedto reduce bits and improve compression efficiency.

For example, and continuing to refer to FIG. 2, CPMV0 _(i), CPMV1 _(i),and CPMV2 _(i) may be three control point motion vectors of a frame ‘i’to be coded. In an exemplary method, CPMV0 _(i-1), representing a vectorcomponent and/or vector determined for a frame previous to a currentframe, including without limitation a reference frame and/or animmediately preceding frame may be used as a prediction or CPMV0 _(i)and a difference between motion vectors may be coded. Difference betweenx and y component of motion vector and its prediction may be coded.

Still referring to FIG. 2, for CPMV(j,i), j, on a range of 0<=j<3 may bea motion vector number, and i, on a range 0<=i<=ref_pic_count, may be areference picture index. ref_pic_count=0 may refers to a currentpicture. CPMV(j,1) may be used as a prediction of CPMV(j,0). Controlpoints for global motion in a frame may be at corners of a frame andCPMV at corresponding corners of frames are likely to be similar andserver as a better prediction.

With continued reference to FIG. 2, and as a non-limiting example, amore complex motion vector prediction may use CPMV for all availablereference pictures in list. In this exemplary method, CPMV(j,i) may beused as a prediction of CPMV(j,0). In this case, an index i may also becoded along with motion vector differences.

Still referring to FIG. 2, previously coded CPMV may be used as aprediction to encode a subsequent CPMV, which may be the next CPMV. Forexample, CPMV(j,i−1), may be used as a prediction of CPMV(j,i). In thiscase, an index i may also be coded along with motion vector differences.When only one set CPMV are coded, CPMV0 may be a prediction for CPMV1and CPMV2.

Further referring to FIG. 2, and as a non-limiting example, table 5shows an example PPS with global motion parameters using control pointmotion vectors.

Descriptor pps_global_motion_parameters_mvd ( ) { motion_model_used u(2)mv0_x se(v) mv1_y se(v) if(motion_model_used == 1){ mv1_x − mv0_x se(v)mv1_y − m01_y se(v) } if(motion_model_used == 2){ mv2_x − mv0_x se(v)mv2_y − m01_y se(v) } }

Table 6 shows another example PPS with differentially coded globalmotion parameters for one or more frames in a reference picture list.

Descriptor pic_parameter_set_rbsp( ) { pps_pic_parameter_set_id ue(v)pps_seq_parameter_set_id ue(v) • • • ref_pic_count u(4) for(i=1; i <=ref_pic count; i++){ gmc_present[i] u(1) } for(i=1; i <= ref_pic_count;i++){ if(gmc_present[i]) mvp = get_cpmv_pred(i);pps_global_motion_parameters_mvp (mvp ) } rbsp_trailing_bits( ) }

With continued to reference to FIG. 2, the following is example pseudocode for deriving a predicted CPMV according to an exampleimplementation:

get_cpmv_pred(i, j){ if(i == 0){ if(j == 0){ pmv.x = 0; pmv.y = 0;}else{ pmv.x = mv0_x; pmv.y = mv0_y; } }else{ pmv[j] = cpmv(j, i−1) }return pmv; }

In many instances, and still referring to FIG. 2, global motion may belikely to be present for a set of frames. Global motion may beterminated upon a scene change or when camera motion stops. Accordingly,a global motion of successive frames is likely to be similar. In someimplementations, if global motion is used in a previous frame, a CPMV ofthe previous frame is likely to be a good predictor thereby reducingmotion vector difference and a bits required to code a motion vector.

In some implementation, and continuing to refer to FIG. 2, it ispossible to implicitly code a zero residual for the global motion vectorresidual by adopting a prior frame's global motion information. Forexample, if global motion is enabled and if a global motion skip mode(e.g., global_motion_skip flag) is enabled, then global motioninformation of a prior frame may be adopted by a current frame as thecurrent frame's global motion. In some implementations, an index may beprovided to the reference list (e.g., list) indicating from whichreference frame motion information may be adopted.

FIG. 3 is a process flow diagram illustrating an example process 300 ofpredicting global motion vectors in a current frame from previouslyencoded global motion vectors of a previous frame. At step 305, acurrent block is received by a decoder. Current block may be containedwithin a bitstream that a decoder receives. Bitstream may include, forexample, data found in a stream of bits that is an input to a decoderwhen using data compression. Bitstream may include information necessaryto decode a video. Receiving may include extracting and/or parsing ablock and associated signaling information from bit stream. In someimplementations, a current block may include a coding tree unit (CTU), acoding unit (CU), or a prediction unit (PU).

At step 310, and still referring to FIG. 3, a residual of a controlpoint motion vector for a current frame may be extracted from bitstream.At step 315, a residual of the control point motion vector can becombined with a prediction of the control point motion vector for thecurrent frame.

FIG. 4 is a system block diagram illustrating an example decoder 400capable of decoding a bitstream 428 with predicting global motionvectors in a current frame from previously encoded global motion vectorsof a previous frame. Decoder 400 may include an entropy decoderprocessor 404, an inverse quantization and inverse transformationprocessor 408, a deblocking filter 412, a frame buffer 416, motioncompensation processor 420 and/or intra prediction processor 424.

In operation, and still referring to FIG. 4, bit stream 428 may bereceived by a decoder 400 and input to entropy decoder processor 404,which entropy decodes portions of a bit stream into quantizedcoefficients. Quantized coefficients may be provided to inversequantization and inverse transformation processor 408, which may performinverse quantization and inverse transformation to create a residualsignal, which may be added to the output of motion compensationprocessor 420 or intra prediction processor 424 according to aprocessing mode. An output of motion compensation processor 420 andintra prediction processor 424 may include a block prediction based on apreviously decoded block. A sum of prediction and residual may beprocessed by deblocking filter 630 and stored in a frame buffer 640.

FIG. 5 is a process flow diagram illustrating an exemplary embodiment ofa process 200 of encoding a video with predicting global motion vectorsin a current frame from previously encoded global motion vectors of aprevious frame according to some aspects of a current subject matterthat may reduce encoding complexity while increasing compressionefficiency. At step 505, a video frame may undergo initial blocksegmentation, for example, using a tree-structured macro blockpartitioning scheme that may include partitioning a picture frame intoCTUs and CUs. At step 510, a residual of a control point motion vectorfor a current frame may be determined. At step 515, a block may beencoded and included in bitstream. Encoding may include utilizing interprediction and intra prediction modes, for example.

FIG. 6 is a system block diagram illustrating an example video encoder600 capable of predicting global motion vectors in a current frame frompreviously encoded global motion vectors of a previous frame accordingto some aspects of current subject matter. Example video encoder 600 mayreceive an input video 604, which may be initially segmented or dividingaccording to a processing scheme, such as a tree-structured macro blockpartitioning scheme (e.g., quad-tree plus binary tree). An example of atree-structured macro block partitioning scheme may include partitioninga picture frame into large block elements called coding tree units(CTU). In some implementations, each CTU may be further partitioned oneor more times into a number of sub-blocks called coding units (CU). Afinal result of this portioning may include a group of sub-blocks thatmay be called predictive units (PU). Transform units (TU) may also beutilized.

An example video encoder 600 may include an intra prediction processor415, a motion estimation/compensation processor 612 (also referred to asan inter prediction processor) capable of supporting prediction ofglobal motion vectors in a current frame from previously encoded globalmotion vectors of a previous frame according to some aspects of currentsubject matter, a transform/quantization processor 616, an inversequantization/inverse transform processor 620, an in-loop filter 624, adecoded picture buffer 628, and/or an entropy coding processor 632. Bitstream parameters may be input to the entropy coding processor 632 forinclusion in the output bit stream 636.

In operation, and still referring to FIG. 6, for each block of a frameof an input video 604, whether to process a block via intra pictureprediction or using motion estimation/compensation may be determined. Ablock may be provided to an intra prediction processor 608 or a motionestimation/compensation processor 612. If block is to be processed viaintra prediction, an intra prediction processor 608 may performprocessing to output a predictor. If block is to be processed via motionestimation/compensation, a motion estimation/compensation processor 612can perform processing including predicting global motion vectors in acurrent frame from previously encoded global motion vectors of aprevious frame according to some aspects of the current subject matter,if applicable.

Further referring to FIG. 6, a residual may be formed by subtracting apredictor from the input video. Residual may be received bytransform/quantization processor 616, which may perform transformationprocessing (e.g., discrete cosine transform (DCT)) to producecoefficients, which may be quantized. Quantized coefficients and anyassociated signaling information may be provided to the entropy codingprocessor 632 for entropy encoding and inclusion in an output bit stream636. Entropy encoding processor 632 may support encoding of signalinginformation related to encoding a current block. In addition, quantizedcoefficients may be provided to inverse quantization/inversetransformation processor 620, which may reproduce pixels, which may becombined with predictor and processed by in loop filter 624, an outputof which may be stored in a decoded picture buffer 628 for use by amotion estimation/compensation processor 612 that is capable ofpredicting global motion vectors in a current frame from previouslyencoded global motion vectors of a previous frame according to someaspects of the current subject matter.

Still referring to FIG. 6, although a few variations have been describedin detail above, other modifications or additions are possible. Forexample, in some implementations, current blocks may include anysymmetric blocks (8×8, 16×16, 32×32, 64×64, 128×128, and the like) aswell as any asymmetric block (8×4, 16×8, and the like).

In some implementations, and continuing to refer to FIG. 6, a quadtreeplus binary decision tree (QTBT) may be implemented. In QTBT, at aCoding Tree Unit level, partition parameters of QTBT may be dynamicallyderived to adapt to local characteristics without transmitting anyoverhead. Subsequently, at Coding Unit level, a joint-classifierdecision tree structure may eliminate unnecessary iterations and controlthe risk of false prediction. In some implementations, LTR frame blockupdate mode may be available as an additional option available at everyleaf node of the QTBT.

In some implementations, and still referring to FIG. 6, additionalsyntax elements may be signaled at different hierarchy levels of thebitstream. For example, a flag may be enabled for an entire sequence byincluding an enable flag coded in a Sequence Parameter Set (SPS).Further, a CTU flag may be coded at a coding tree unit (CTU) level.

It is to be noted that any one or more of the aspects and embodimentsdescribed herein may be conveniently implemented using digitalelectronic circuitry, integrated circuitry, specially designedapplication specific integrated circuits (ASICs), field programmablegate arrays (FPGAs) computer hardware, firmware, software, and/orcombinations thereof, as realized and/or implemented in one or moremachines (e.g., one or more computing devices that are utilized as auser computing device for an electronic document, one or more serverdevices, such as a document server, etc.) programmed according to theteachings of the present specification, as will be apparent to those ofordinary skill in the computer art. These various aspects or featuresmay include implementation in one or more computer programs and/orsoftware that are executable and/or interpretable on a programmablesystem including at least one programmable processor, which may bespecial or general purpose, coupled to receive data and instructionsfrom, and to transmit data and instructions to, a storage system, atleast one input device, and at least one output device. Appropriatesoftware coding may readily be prepared by skilled programmers based onthe teachings of the present disclosure, as will be apparent to those ofordinary skill in the software art. Aspects and implementationsdiscussed above employing software and/or software modules may alsoinclude appropriate hardware for assisting in the implementation of themachine executable instructions of the software and/or software module.

Such software may be a computer program product that employs amachine-readable storage medium. A machine-readable storage medium maybe any medium that is capable of storing and/or encoding a sequence ofinstructions for execution by a machine (e.g., a computing device) andthat causes the machine to perform any one of the methodologies and/orembodiments described herein. Examples of a machine-readable storagemedium include, but are not limited to, a magnetic disk, an optical disc(e.g., CD, CD-R, DVD, DVD-R, etc.), a magneto-optical disk, a read-onlymemory “ROM” device, a random access memory “RAM” device, a magneticcard, an optical card, a solid-state memory device, an EPROM, an EEPROM,Programmable Logic Devices (PLDs), and/or any combinations thereof. Amachine-readable medium, as used herein, is intended to include a singlemedium as well as a collection of physically separate media, such as,for example, a collection of compact discs or one or more hard diskdrives in combination with a computer memory. As used herein, amachine-readable storage medium does not include transitory forms ofsignal transmission.

Such software may also include information (e.g., data) carried as adata signal on a data carrier, such as a carrier wave. For example,machine-executable information may be included as a data-carrying signalembodied in a data carrier in which the signal encodes a sequence ofinstruction, or portion thereof, for execution by a machine (e.g., acomputing device) and any related information (e.g., data structures anddata) that causes the machine to perform any one of the methodologiesand/or embodiments described herein.

Examples of a computing device include, but are not limited to, anelectronic book reading device, a computer workstation, a terminalcomputer, a server computer, a handheld device (e.g., a tablet computer,a smartphone, etc.), a web appliance, a network router, a networkswitch, a network bridge, any machine capable of executing a sequence ofinstructions that specify an action to be taken by that machine, and anycombinations thereof. In one example, a computing device may includeand/or be included in a kiosk.

FIG. 7 shows a diagrammatic representation of one embodiment of acomputing device in the exemplary form of a computer system 700 withinwhich a set of instructions for causing a control system to perform anyone or more of the aspects and/or methodologies of the presentdisclosure may be executed. It is also contemplated that multiplecomputing devices may be utilized to implement a specially configuredset of instructions for causing one or more of the devices to performany one or more of the aspects and/or methodologies of the presentdisclosure. Computer system 700 includes a processor 704 and a memory708 that communicate with each other, and with other components, via abus 712. Bus 712 may include any of several types of bus structuresincluding, but not limited to, a memory bus, a memory controller, aperipheral bus, a local bus, and any combinations thereof, using any ofa variety of bus architectures.

Memory 708 may include various components (e.g., machine-readable media)including, but not limited to, a random-access memory component, a readonly component, and any combinations thereof. In one example, a basicinput/output system 716 (BIOS), including basic routines that help totransfer information between elements within computer system 700, suchas during start-up, may be stored in memory 708. Memory 708 may alsoinclude (e.g., stored on one or more machine-readable media)instructions (e.g., software) 720 embodying any one or more of theaspects and/or methodologies of the present disclosure. In anotherexample, memory 708 may further include any number of program modulesincluding, but not limited to, an operating system, one or moreapplication programs, other program modules, program data, and anycombinations thereof.

Computer system 700 may also include a storage device 724. Examples of astorage device (e.g., storage device 724) include, but are not limitedto, a hard disk drive, a magnetic disk drive, an optical disc drive incombination with an optical medium, a solid-state memory device, and anycombinations thereof. Storage device 724 may be connected to bus 712 byan appropriate interface (not shown). Example interfaces include, butare not limited to, SCSI, advanced technology attachment (ATA), serialATA, universal serial bus (USB), IEEE 1394 (FIREWIRE), and anycombinations thereof. In one example, storage device 724 (or one or morecomponents thereof) may be removably interfaced with computer system 700(e.g., via an external port connector (not shown)). Particularly,storage device 724 and an associated machine-readable medium 728 mayprovide nonvolatile and/or volatile storage of machine-readableinstructions, data structures, program modules, and/or other data forcomputer system 700. In one example, software 720 may reside, completelyor partially, within machine-readable medium 728. In another example,software 720 may reside, completely or partially, within processor 704.

Computer system 700 may also include an input device 732. In oneexample, a user of computer system 700 may enter commands and/or otherinformation into computer system 700 via input device 732. Examples ofan input device 732 include, but are not limited to, an alpha-numericinput device (e.g., a keyboard), a pointing device, a joystick, agamepad, an audio input device (e.g., a microphone, a voice responsesystem, etc.), a cursor control device (e.g., a mouse), a touchpad, anoptical scanner, a video capture device (e.g., a still camera, a videocamera), a touchscreen, and any combinations thereof. Input device 732may be interfaced to bus 712 via any of a variety of interfaces (notshown) including, but not limited to, a serial interface, a parallelinterface, a game port, a USB interface, a FIREWIRE interface, a directinterface to bus 712, and any combinations thereof. Input device 732 mayinclude a touch screen interface that may be a part of or separate fromdisplay 736, discussed further below. Input device 732 may be utilizedas a user selection device for selecting one or more graphicalrepresentations in a graphical interface as described above.

A user may also input commands and/or other information to computersystem 700 via storage device 724 (e.g., a removable disk drive, a flashdrive, etc.) and/or network interface device 740. A network interfacedevice, such as network interface device 740, may be utilized forconnecting computer system 700 to one or more of a variety of networks,such as network 744, and one or more remote devices 748 connectedthereto. Examples of a network interface device include, but are notlimited to, a network interface card (e.g., a mobile network interfacecard, a LAN card), a modem, and any combination thereof. Examples of anetwork include, but are not limited to, a wide area network (e.g., theInternet, an enterprise network), a local area network (e.g., a networkassociated with an office, a building, a campus or other relativelysmall geographic space), a telephone network, a data network associatedwith a telephone/voice provider (e.g., a mobile communications providerdata and/or voice network), a direct connection between two computingdevices, and any combinations thereof. A network, such as network 744,may employ a wired and/or a wireless mode of communication. In general,any network topology may be used. Information (e.g., data, software 720,etc.) may be communicated to and/or from computer system 700 via networkinterface device 740.

Computer system 700 may further include a video display adapter 752 forcommunicating a displayable image to a display device, such as displaydevice 736. Examples of a display device include, but are not limitedto, a liquid crystal display (LCD), a cathode ray tube (CRT), a plasmadisplay, a light emitting diode (LED) display, and any combinationsthereof. Display adapter 752 and display device 736 may be utilized incombination with processor 704 to provide graphical representations ofaspects of the present disclosure. In addition to a display device,computer system 700 may include one or more other peripheral outputdevices including, but not limited to, an audio speaker, a printer, andany combinations thereof. Such peripheral output devices may beconnected to bus 712 via a peripheral interface 756. Examples of aperipheral interface include, but are not limited to, a serial port, aUSB connection, a FIREWIRE connection, a parallel connection, and anycombinations thereof.

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope of this invention.Features of each of the various embodiments described above may becombined with features of other described embodiments as appropriate inorder to provide a multiplicity of feature combinations in associatednew embodiments. Furthermore, while the foregoing describes a number ofseparate embodiments, what has been described herein is merelyillustrative of the application of the principles of the presentinvention. Additionally, although particular methods herein may beillustrated and/or described as being performed in a specific order, theordering is highly variable within ordinary skill to achieve embodimentsas disclosed herein. Accordingly, this description is meant to be takenonly by way of example, and not to otherwise limit the scope of thisinvention.

In the descriptions above and in the claims, phrases such as “at leastone of” or “one or more of” may occur followed by a conjunctive list ofelements or features. The term “and/or” may also occur in a list of twoor more elements or features. Unless otherwise implicitly or explicitlycontradicted by the context in which it is used, such a phrase isintended to mean any of the listed elements or features individually orany of the recited elements or features in combination with any of theother recited elements or features. For example, the phrases “at leastone of A and B;” “one or more of A and B;” and “A and/or B” are eachintended to mean “A alone, B alone, or A and B together.” A similarinterpretation is also intended for lists including three or more items.For example, the phrases “at least one of A, B, and C;” “one or more ofA, B, and C;” and “A, B, and/or C” are each intended to mean “A alone, Balone, C alone, A and B together, A and C together, B and C together, orA and B and C together.” In addition, use of the term “based on,” aboveand in the claims is intended to mean, “based at least in part on,” suchthat an unrecited feature or element is also permissible.

The subject matter described herein can be embodied in systems,apparatus, methods, and/or articles depending on the desiredconfiguration. The implementations set forth in the foregoingdescription do not represent all implementations consistent with thesubject matter described herein. Instead, they are merely some examplesconsistent with aspects related to the described subject matter.Although a few variations have been described in detail above, othermodifications or additions are possible. In particular, further featuresand/or variations can be provided in addition to those set forth herein.For example, the implementations described above can be directed tovarious combinations and sub-combinations of the disclosed featuresand/or combinations and sub-combinations of several further featuresdisclosed above. In addition, the logic flows depicted in theaccompanying figures and/or described herein do not necessarily requirethe particular order shown, or sequential order, to achieve desirableresults. Other implementations may be within the scope of the followingclaims.

What is claimed is:
 1. A decoder, the decoder comprising circuitryconfigured to: receive a bitstream; extract a residual of a controlpoint motion vector for a current frame from the bitstream; and combinethe residual of the control point motion vector with a prediction of thecontrol point motion vector for the current frame.
 2. The decoder ofclaim 1, further configured to decode the current frame.
 3. The decoderof claim 1, further configured to determine the prediction of thecontrol point motion vector.
 4. The decoder of claim 1, wherein thecontrol point motion vector includes a translational motion vector. 5.The decoder of claim 1, wherein the control point motion vector is avector of a four parameter affine motion model.
 6. The decoder of claim1, wherein the control point motion vector is a vector of a sixparameter affine motion model.
 7. The decoder of claim 1, furthercomprising: an entropy decoder processor configured to receive the bitstream and decode the bitstream into quantized coefficients; an inversequantization and inverse transformation processor configured to processthe quantized coefficients including performing an inverse discretecosine; a deblocking filter; a frame buffer; and an intra predictionprocessor.
 8. The decoder of claim 1, wherein the current frame includesa current block that forms part of a quadtree plus binary decision tree.9. The decoder of claim 1, wherein the current frame includes a currentblock that is a coding tree unit.
 10. The decoder of claim 1, whereinthe current frame includes a current block that is a coding unit.
 11. Amethod comprising: receiving, by a decoder, a bitstream; extracting aresidual of a control point motion vector for a current frame and fromthe bitstream; and combining the residual of the control point motionvector with a prediction of the control point motion vector for thecurrent frame.
 12. The method of claim 11, further comprising decodingthe current frame.
 13. The method of claim 11, further comprisingdetermining the prediction of the control point motion vector.
 14. Themethod of claim 11, wherein the control point motion vector is atranslational motion vector.
 15. The method of claim 11, wherein thecontrol point motion vector is a vector of a four parameter affinemotion model.
 16. The method of claim 11, wherein the control pointmotion vector is a vector of a six parameter affine motion model. 17.The method of claim 11, the decoder further comprising: an entropydecoder processor configured to receive the bit stream and decode thebitstream into quantized coefficients; an inverse quantization andinverse transformation processor configured to process the quantizedcoefficients including performing an inverse discrete cosine; adeblocking filter; a frame buffer; and an intra prediction processor.18. The method of claim 11, wherein the current frame includes a currentblock that forms part of a quadtree plus binary decision tree.
 19. Themethod of claim 11, wherein the current frame includes a current blockthat is a coding tree unit.
 20. The method of claim 11, wherein thecurrent frame includes a current block that is a coding unit.